The preferred embodiments relate to ultrasound transducers and, more particularly, to combined discrete transmitter circuitry with a separate ultrasonic transducer receiver array.
Ultrasound transducers are known in the art for transmitting ultrasound waves and detecting a reflection or echo of the transmitted wave. Such devices are also sometimes referred to as ultrasound or ultrasonic transducers or transceivers. Ultrasound transducers have myriad uses, including consumer devices, vehicle safety, and medical diagnostics. In these and other fields, signals detected by the transducer may be processed to determine distance which may be further combined with directional or area processing to determine shape as well as aspects in connection with two and three dimensional processing, including image processing.
A micromachined ultrasonic transducer (MUT) array is commonly used in the prior art as an ultrasound transducer, that is, to perform both the transmission of ultrasonic sounds and the detection of the sound echo. Such an array is typically formed using semiconductor processing, whereby an array of micromachined mechanical elements is created relative to the semiconductor substrate. Each array element has a same construction but is separately excitable to transmit a signal and separately readable to detect the signal echo. The prior art includes numerous techniques for forming numerous types of elements, where two common element examples are piezoelectric or capacitive, the former used for a so-called piezoelectric micromachined ultrasonic transducer (pMUT) and the latter used for a so-called capacitive micromachined ultrasonic transducer (cMUT). In general, the pMUT array elements function in response to the known nature of piezoelectric materials combined sometimes with a thin film membrane, which collectively generate electricity from applied mechanical strain and, in a reversible process, generate a mechanical strain from applied electricity. Also in general, the cMUT array elements function in response to the known nature of capacitive structure and in combination with an associated membrane, so the elements generate an alternating electrical signal from a change in capacitance caused by vibration of the membrane and, in a reversible process, generate vibration of the membrane from an applied alternating signal across the capacitor.
While the above and related approaches have served various needs in the prior art, they also provide various drawbacks. For example, acoustic power is a function of the product of pressure, area, and velocity, so the membrane used in a MUT may limit the transmission power because of limitations in sustaining pressure, a relatively small areal coverage on part of the transducer surface, and also due to reduced velocity form non-uniformities across the membrane. As another example, the number of elements in the MUT array are often increased so as to achieve greater resolution or other performance, and wire bonding, flex cable, or the like are often implemented for interconnectivity to each element, so a large number of elements (e.g., 50×50 or above) creates considerable complexity and cost in a wire bundle or cable so as to electrically communicate with all elements.
Given the preceding, the present inventors seek to improve upon the prior art, as further detailed below.